[1.6.x] Noted that localmem is the default cache.
[1.6.x] Noted that localmem is the default cache.

Backport of c456ea4ec8 from master

django-nonrel/django,felixjimenez/django,redhat-openstack/django,redhat-openstack/django,django-nonrel/django,dex4er/django,felixjimenez/django,dex4er/django,django-nonrel/django,dex4er/django,redhat-openstack/django,felixjimenez/django,felixjimenez/django,django-nonrel/django,redhat-openstack/django